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Co-seismic Surface Dilatation and Shear Strain Fields Derived from SPOT-5 Displacements

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posted on 23.02.2021, 13:24 by Guo Cheng, William Barnhart
Repeated earthquake cycles produce topography, fault damage zones, and other geologic structures along faults. These geomorphic and structural features indicate the presence of co-seismic permanent (inelastic) surface deformation, yet a long-standing question in earthquake research is how much of the co-seismic deformation field is elastic versus inelastic. These questions arise in part because it is unclear what measurable co-seismic characteristics, such as off-fault or distributed surface deformation and cracking, represent true unrecoverable deformation. One emerging descriptor of permanent co-seismic deformation is surface strain magnitudes inferred from imaging geodesy observations. In this study, we present the surface strain field of the 2013 Mw7.7 Baluchistan strike-slip earthquake in southern Pakistan. We invert co-seismic displacement fields generated from pixel-tracking of SPOT-5 and WorldView optical imagery for co-seismic surface horizontal strain tensors. We observe that co-seismic strain field is dominated by negative dilatation strains, indicating that the co-seismic fault zone contracted during the earthquake. We show that co-seismic inelastic failure exhibits a relatively consistent width along the rupture that is localized to a zone 100-200 m wide on the hanging wall side. The width of co-seismic permanent deformation does not correlate with variations in off-fault deformation or surface geology. Based on comparisons to other recent earthquakes, we posit that the permanent surface strains reflect inelastic deformation of the faults inner damage zone, and that the width of this zone reflects fault maturity.

Funding

DISTRIBUTED STRAIN IN SOUTHERN PAKISTAN HOW AND WHY DO SINGLE FAULTS SLIP IN MULTIPLE DIRECTIONS?\NFAULTS ARE FUNDAMENTAL INDICATORS OF STRAIN ORIENTATION AND ACCOMMODATION IN ZONES OF ACTIVE DEFORMATION, AND FAULT SLIP ANALYSIS ILLUMINATES LONG TERM PLA

National Aeronautics and Space Administration

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Probing the transient rheology of accretionary prisms and megathrust earthquake hazard in the Indian Ocean basin

Directorate for Geosciences

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History

Publisher

4TU.ResearchData

Geolocation

Baluchistan

Organizations

University of Iowa, Department of Earth and Environmental Sciences, USA

Licence

Exports